I'm looking for guidance on how to:
1) soften the bellow. My B&J bellow is very stiff, I'm not sure if I can use Lexol Leather Conditioner on the bellow.
2) Revolving Back: can I disassemble and clean/relube it.

Lexol may leave a sticky residue.
Neatsfoot oil, available at Tandy leather.
And as Banjo said Pledge Natural Beauty (yellow can)._________________The best camera ever made is the one that YOU enjoy using and produces the image quality that satifies YOU.

There was a time when Lemon Pledge was available in a non-aerosol plastic bottle with manual spritzer. I still have such a bottle from years gone by, and I even have occasion to use it from time to time. It made an excellent slide lubricant for my trombone, although its effectiveness didn't last very long before it gummed up. I've used it on the red bellows of my Century, with good results.

I don't have a clue how B&J did their back.
If the back is removable from the camera remove it.
On the inside there may be screws that you remove to separate the the back sections. Remove those screws and carefully separate the back sections.
Clean the sections with alcohol, lube with a just detectable layer of white lithium grease and reassemble.
Use a digital camera to take pictures as you disassemble.

If the back uses nylon guides as the Super Graphics backs do then solvents and oils can damage the parts.

3in1 oil and WD 40 dry out quickly and leave a sticky residue.
TriFlow, watch oil or gun oil work well on cameras._________________The best camera ever made is the one that YOU enjoy using and produces the image quality that satifies YOU.

Try putting a 2 to 3 drops of oil in at the rotation release and rotate several times in both directions. Rotate 180° and oil as before and rotate some more._________________The best camera ever made is the one that YOU enjoy using and produces the image quality that satifies YOU.

With the bellows removed from the camera extend and clamp them to a flat work surface. Measure the bellows and cut the pneumatic cloth to fit the inside of the bellows allowing for 1/2 to 1 inch overlap. Fold the cloth so that the rubber coating is the outer surface. Off setting the original seam coat one side of the inside of the bellows with the contact cement and while wet place the pneumatic cloth on the inside and press into place. Continue working around the bellows applying glue and unrolling the pneumatic cloth and pressing into place eliminating air pockets and wrinkles until the entire bellows is covered. Allow to dry. Dry glue not between the material will rub off. Starting at the rear refold the bellows according to the original folds. Reinstall into the camera. This works on torn and riped bellows.

1 inch foam brushes work well to spread the glue._________________The best camera ever made is the one that YOU enjoy using and produces the image quality that satifies YOU.

would this increase the thickness of the bellow and make it hard to fold back into the camera? OR maybe I did not understand your instruction fully, especially this line "Off setting the original seam coat one side of the inside of the bellows with the contact cement and while wet place the pneumatic cloth on the inside and press into place."

It makes them thicker when folded but on a 26 inch bellows it only gained 1/4 inch or so fully compressed. Installing a second lining making its seam on top of the existing one will add extra unwanted thickness.

When cutting center the front perimeter measurement on the rear perimeter measurement and the sides will have the correct taper of the bellows.

The Anniversary Speed I'm repairing has 26 pleats in its bellows. .008*26=.208=.023 less than 13/64_________________The best camera ever made is the one that YOU enjoy using and produces the image quality that satifies YOU.